modded server when my friend joins it says wrong version

[Taueyy]

we have both got the same mods but when he joins me it tells him he was the wrong version or something?

[Lәoи «]

It says this?: “The server host is playing on version 9999 while you are on version 45”

[Blawg]

i had this problem and it turned out my mod was updated while my friends wasnt, make sure you are all using the latest mods